Each person is different. So it simply depends on if you are the type that can simply walk into a shop and pick something of the flash wall (which plenty of people do im just not one of them) or if you need to have a design that is totally you and no one else.
I will say that there is almost no way to be entirely original because there are so many tattoos out there almost everything has been done so don't get too upset if you see someone down the road that has one similar to yours.
As for picking one, the way I have always gone for myself is what tattoo will best tell the story of what is going on in my life at that time. That way, fifty years down the road even if it has faded over time I can still say that its there for a reason. Some tattoos may look stupid to others but as long as it was a chapter in my life I couldnt care less what they think and suggest the same to you.
Hope I helped a little.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.